Significant increase in performance of electronic apparatuses such as computers in recent years has also been increasing the amounts of heat generated by semiconductor devices such as central processing units (CPUs). An air-cooling system and a water-cooling system are used for cooling semiconductor devices. To cool a semiconductor device that generates a large amount of heat, the water-cooling system is often employed.
The cooling device of the water-cooling system is designed as follows. A cooling device, which is called as a cooling plate, is attached to an upper surface (hereinafter, referred to as a “heat radiating surface”) of a semiconductor device, and a heat dissipating device is disposed at a position separated from the cooling device. The cooling device and the heat dissipating device are connected by a pipe (or a tube). A flow passage through which a coolant flows is provided inside the cooling device. The coolant is thus circulated between the cooling device and the heat dissipating device through the flow passage, thereby transporting heat generated by the semiconductor device to the heat dissipating device. The heat is thus dissipated from the heat dissipating device to the atmosphere. Note that in the present application, water or another fluid (heat medium) used for transporting heat from the cooling device to the heat dissipating device is referred to as a coolant.
A general cooling device is provided with a flow passage arranged such that a coolant flows in a zigzag fashion along a heat radiating surface of a semiconductor device, cooling the entire heat radiating surface of the semiconductor device (such a technique is disclosed, for example, in Japanese Laid-open Patent Publication No. 2001-44678). Moreover, another cooling device is proposed which is provided with a flow passage arranged such that a coolant flows in a direction perpendicular to a heat radiating surface of a semiconductor device (such a technique is disclosed, for example, in Published Japanese National Publication of International Patent Application No. 2006-516068).
Furthermore, it is proposed that a thermoelectric conversion element is used to generate electricity from heat generated by a semiconductor device for use as a power source for causing a coolant to flow (such a technique is disclosed, for example, in Japanese Laid-open Patent Publication Nos. 2001-44678 and 2007-227413).